Acid type solid urea-nitric fertilizer

ABSTRACT

The present invention relates to the reaction of phosphate rock with nitric acid and urea to produce nitrogen-phosphorus containing slurries, which slurries, in turn, may be granulated and dried to produce solid N-P fertilizer products with agronomically advantageous low pHs (1.0-4.0). The products have excellent storage characteristics. The improved properties of these products result partially from the formation of a new compound, Ca(H 2  PO 4 )(NO 3 ).CO(NH 2 ) 2 , which was discovered during the course of the investigation that led to the instant invention.

The invention herein described may be manufactured and used by or forthe Government for governmental purposes without the payment to us ofany royalty therefor.

This application is a continuation-in-part of application Ser. No.612,162, filed May 21, 1984, for PROCESS FOR THE PRODUCTION OF SOLIDUREA-NITRIC PHOSPHATE FERTILIZER PRODUCTS.

INTRODUCTION

The phosphate content of phosphatic ores is generally too insoluble fordirect utilization by food-producing crops. Current phosphate fertilizertechnology within the United States generally involves the reaction ofphosphate ores with sulfuric acid to produce soluble phosphaticmaterials which may be further processed to produce a variety offertilizer products. The sole function of the sulfuric acid is tosolubilize the phosphate content of the ore while converting the calciumcomponent to an insoluble calcium sulfate salt, usually gypsum(CaSO₄.2H₂ O). Normally about five tons of gypsum is produced for eachton of P₂ O₅ solubilized. This calcium sulfate byproduct is generally oflittle agronomic or commercial value and serves as a disposal and waterpollution problem for the industry.

Oftentimes the cost of sulfur for sulfuric acid production dictates thatthe use of nitric acid as an acidulant for the processing of suchphosphate ore be economically advantageous. Nitric acid offers anadvantage over sulfuric acid in that it not only solubilizes thephosphatic component of the ore, but also supplies a nitrogen-containinganion (nitrate, NO₃ ⁻) which may itself be incorporated in a finalfertilizer product. Nitric phosphate processes are quite highlydeveloped and are extensively used in the European countries. In manyinstances, the production cost of nitric phosphate fertilizers is lowerthan equivalent sulfuric acid-based products, depending, of course, onsuch other factors as location, cost, transportation, crops,application, etc.

Although such nitric phosphate fertilizers are characterized by aplethora of advantages over those produced by the acidulation ofphosphate rock with sulfuric acid, they are still fraught with severaldistinct problems and disadvantages as produced by current prior-artpractices. The present invention addresses the elimination of several ofthese significant drawbacks and disadvantages including the productionof products having significantly lower hygroscopicities and higherwater-soluble P₂ O₅ contents per unit of nitric acid employed foracidulation. The incorporation therein of the gangue present in thephosphate ore acidulated in the production thereof, also eliminates thenecessity of dealing with unwanted or unusable byproducts therefrom.Further, in developing the present invention, a new composition ofmatter has been identified and isolated which, because of the nature ofits unusually high critical relative humidity, significantly improvesupon the overall physical properties of the products resulting from thepractice of the instant invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

From a technological standpoint, a major problem associated with thenitric acid acidulation of phosphate rock, as currently practiced,involves the production of the soluble byproduct, calcium nitrate, whichrenders the fertilizer products hygroscopic and generally difficult tostore. Furthermore, the presence of soluble calcium causes the reversionof phosphate to low-water and citrate-soluble forms (dicalcium phosphateand apatite) when the resulting acidulates are subsequently neutralizedwith ammonia and granulated to produce solid N-P fertilizer products. Inpractice, these problems may be circumvented by removal of part of thecalcium by refrigeration-crystallization (Odda Process); by reaction ofthe calcium with supplemental phosphoric acid (Phosphonitric Process);or by precipitation with sulfate (Sulfonitric Process) [A. V. Slack etal., Farm Chemicals, Vol. 130, Nos. 4, 5, 6 and 7 (April, May, June, andJuly, 1976)]. However, refrigeration-crystallization processes arecomplex and require high capital investment per ton of product and highoperating cost because of high energy requirements. Also, it isdifficult to economically dispose of some of the byproducts (calciumcarbonate or gypsum) from the other processes.

2. Prior Art

A number of prior-art investigations concerning the reactions of nitricacid and urea with phosphate ore have been reported in the scientificand patent literature. Initial work was conducted by Nagai and hiscoworkers in the early 1950s [S. Nagai and T. Kanasawa, J. Chem. Soc.,Japan, Ind. Chem. Sect., 54, 39 (1951); S. Nagai, T. Kanasawa, and K.Saito, J. Chem. Soc. Japan Ind. Chem. Sect., 54, 210 (1951); S. Nagai,T. Kanasawa, and K. Sakurada, J. Chem. Soc. Japan, Ind. Chem. Sect., 54,611 (1951)]. These workers investigated the properties of reactionproducts produced in the pure component system Ca₃ (PO₄)₂ --CO(NH₂)₂--HNO₃ and determined that the urea adducts: "cal urea" [CaNO₃.4CO(NH₂)₂], and urea nitrate [CO(NH₂)₂.HNO₃ ] were the primary reaction products.They further extended their studies to include the addition of variousquantities of urea to nitric acid acidulates of phosphate ore andconcluded that products containing about 24- 25 percent total N(urea-N˜19-20 percent, NO₃ -N˜4.5 percent) and about 9-10 percent P₂ O₅offered the best physical properties for consideration as possible N-Pfertilizer products. However, the critical relative humidities of thesematerials were not reported.

Japanese patents No. Sho 26-767, February 1951, and No. Sho 28-3169,July 1951, describe processes for the acidulation of phosphate ore withnitric acid followed by the addition of urea and calcium or potassiumsalts to produce nonhygroscopic granular fertilizers.

Guillet et al, in French Pat. No. 1,107,730, January 1956, describe thereaction of urea with hydrated calcium nitrate containing nitric andphosphoric acids to produce Ca(NO₃)₂.4CO(NH₂)₂. This product was used incombination with Ca⁺², NH₄ ⁺¹, and P₂ O₅ containing salts to produce N-Pfertilizers. Further work (French Pat. No. 1,182,058, June 1959)describes the reaction of phosphate rock with HNO₃ and urea to give animproved N-P fertilizer containing a complex mixture of urea calciumnitrate [Ca(NO₃)₂.(CO(NH₂)₂)₄ ], urea phosphate [CO(NH₂)₂.H₃ PO₄ ], ureanitrate [CO(NH₂)₂.HNO₃ ], and dicalcium phosphate (CaHPO₄). The improvedphysical properties of this N-P fertilizer material resulted from theformation of urea adducts with nitrate, phosphate, and calcium presentwithin the solid reaction mixture.

In 1963 Russian investigators [Ya. S., Shenken, V. A. Klevke, and B. G.Lyudkovskaya, Dokl. Akad. Nuak. SSSR 149, 656-9 (1963)] studied mixturesof calcium nitrate, phosphoric acid, and urea at 1:1 ratios of urea tophosphoric acid and calcium nitrate. The primary products were ureanitrate [CO(NH₂)₂.HNO₃ ] and monocalcium phosphate [Ca(H₂ PO₄)₂.H₂ O].Addition of more urea resulted in the formation of Ca(NO₃)₂.4CO(NH₂)₂.

In 1964 this Russian study, supra, was extended to include an x-ray andthermodynamic investigation [Ya. S. Shenkin and V. A. Klevke, Khim.Prom-st, No. 1, 57 (1964)] of various Ca(NO₃)₂.4H₂ O, H₃ PO₄, andCO(NH₂)₂ mixtures. This study again showed presence of CO(NH₂)₂.HNO₃,Ca(NO₃)₂.4CO(NH₂)₂, CO(NH₂)₂.H₃ PO₄, CaHPO₄, and Ca(H₂ PO₄)₂.H₂ O asproducts of the reactions and also established the existence ofretrograde equilibria such as: Ca(H₂ PO₄)₂ +Ca(NO₃)₂ +2CO(NH₂)₂⃡2CaHPO+2[CO(NH₂)₂.HNO₃ ]; Ca(H₂ PO₄)₂ +2[CO(NH₂)₂.HNO₃]+4CO(NH₂)⃡(Ca(NO₃)₂.4CO(NH₂)₂ +2[CO(NH₂)₂.H₃ PO₄ ]; and CaHPO₄+2[CO(NH.sub. 2)₂.HNO₃ ]+3CO(NH₂)₂ ⃡Ca(NO₃)₂.4CO(NH₂)₂ +CO(NH₂)₂.H₃ PO₄as water is removed from the system to produce solid products. However,these investigators failed to identify the presence of the new triplecomponent adduct, Ca(H₂ PO₄)(NO₃).CO(NH₂)₂ discovered during the presentinvestigation. This new compound has a very high critical relativehumidity (69 percent), almost as good as pure urea (75 percent), whichimproves the physical properties of the final products tremendously. Inaddition to this, P₂ O₅ in the compound is 92 percent water soluble andcompletely available to plant growth (citrate solubility=100 percent).Also, the new compound is acidic when dissolved in water (pH=3.08) suchthat it possesses all the benefits of other acidic fertilizers.

Subsequently, Frazier et al (A. W. Frazier, J. R. Lehr, and J. P. Smith,Agr. and Food Chem., Vol. 15, No. 2, page 345, Mar./Apr. 1967) were ableto isolate and characterize a new double salt adduct, urea-monocalciumphosphate [Ca(H₂ PO₄)₂.4CO(NH₂)₂ ], from CaO-P₂ O₅ -CO(NH₂)₂ -H₂ Osystems.

Kochemba et al, U.S.S.R. 775,096, October 1980, concerned themselveswith the reaction of phosphate rock with nitric acid followed by theaddition of a SO₄ ⁻ component and urea to produce a N-P fertilizerproduct. This work was followed by a publication (Yu. I., Kochemba andYa. S. Shenkin, Zhurnal Prikladonoi Khimii, Vol. 55, No. 5, pp. 977-980,May 1982) in which KCl and NH₃ are incorporated into the reactionproducts to produce a urea-N-P-K fertilizer.

Stoller, U.S. Pat. No. 4,315,763, describes some of the applications andagronomic advantages of low pH solution fertilizers (<4.0). TheTennessee Valley Authority has conducted extensive research using low pHurea phosphate fertilizers for application on different types of soilsand this research generally shows that there is an agronomic advantagefor the use of low pH fertilizer on some soil systems. The products fromthe instant invention not only have a low pH, but they also contain thehighly valuable nitrate nitrogen source. Nitrate nitrogen is a form ofnitrogen which is less likely to be lost by evaporation and more likelyto be absorbed directly by the roots of a growing crop.

SUMMARY OF THE INVENTION

The instant invention relates to the discovery of a new composition ofmatter having an unusually high critical relative humidity which iscomparable to that exhibited by urea and which imparts to the overallproduct resulting from the practice of the instant invention theadvantage of having significantly improved physical properties over andabove that which may be realized by the practice of prior-art teachingsrelating to the production of solid nitric phosphate fertilizermaterials. As pointed out by Hoffmeister (G. Hoffmeister, "PhysicalProperties of Fertilizers and Methods for Measuring Them," TVA BulletinY-147, October 1979, page 13), the critical relative humidity of a saltis that relative humidity of air at which the partial vapor pressure ofwater in the air exactly equals the equilibrium water vapor pressureabove a saturated solution of the salt at any given temperature. Indeveloping the instant invention, it was discovered that the combinationof urea with nitric acid results in the conversion of phosphate rockultimately to N-P fertilizer products which avoid the plethora ofproblems normally associated with the conversion of phosphate rock withnitric acid or combinations of nitric acids and sulfuric acid followedby the addition of ammonia.

In practicing the dictates of the instant process as it relates to thepresent invention, a new composition of matter was isolated andidentified, which is the triple component adduct, Ca(H₂PO₄)(NO₃).CO(NH₂)₂. This newly discovered adduct exhibits an extremelyhigh critical relative humidity to the point of being comparable to thatattributed to pure urea and results in significantly improving theproduction of the final phosphate fertilizer material and, in addition,all of the P₂ O₅ values in said adduct are water (92%) and citratesoluble (100%) and thus readily available to the growing plant.

OBJECTS OF THE INVENTION

A principal objective of the present invention is to provide anacid-type, economical and simple process which uses nitric acid and ureato convert phosphate rock to solid N-P fertilizer products, while at thesame time avoiding the problems normally associated with the practice ofcurrent available nitric phosphate- and sulfur-based technologies. Theproducts resulting therefrom have low pHs which may have agronomicadvantages when used correctly on crops and soils. In practicing theprocess of the instant invention, care is taken to control reactiontemperatures and ratios of reacting constituents to effect production ofurea-calcium phosphate-calcium nitrate-phosphate acid-nitric acidcomplexes or adducts (one of which was discovered by us) which have muchlower hygroscopicities and pHs than are currently available fromprocesses of the prior art. The product of the instant invention willalso have a much higher water-soluble P₂ O₅ content than normallyproduced by current nitric phosphate processes.

A further object and advantage of the present invention is that in thepractice thereof, all components utilized in the manufacturing process,including the trace metals and quartz or gangue present in the phosphateore, are incorporated in the final products. Hence, no "throw-away"by-products are produced and trace elements (micronutrients) beneficialto growing plants are provided.

In addition to these objects and advantages, the acidic nature of thefertilizer products realized by the practice of the present inventionprovides local "micro sites" of low pH within the soil system which areeffective in preventing the loss of ammonia produced by theurease-promoted hydrolysis of urea [J. K. R. Gasser and A. Penny, J.Agric. Sci., Camb. (1967), 69, 139-146; J. M. Bremner and L. A. Douglas,Soil Sci. Soc. Amer. Proc., Vol. 35, 1971, pp. 575-578].

DESCRIPTION OF THE DRAWING

The present invention, together with further objects and advantagesthereof, will be better understood from a consideration of the followingdescription taken in connection with the accompanying drawing in which:

The FIGURE is a flow diagram of the instant invention process and thepreferred embodiments thereof.

The simplicity and advantages of the instant invention are easilyunderstood by examination of the flow diagram for the process as shownin the FIGURE. Ground phosphate rock and nitric acid from sources notshown are fed via lines 1 and 2, respectively, into reactor 3, whereacidulation is allowed to proceed at temperatures of about 60°-70° C.for a period of time ranging from about 30 minutes to about 2 hours.Subsequently, urea, also from a source not shown, is added via line 4into reactor 3 and therein thoroughly stirred into the acidulate over aperiod of time ranging from about one to about two hours, during whichtime the melt resulting and maintained in reactor 3 is allowed to coolto a temperature ranging from about 35° C. to about 45° C. Analternative procedure involves the simultaneous addition of phosphaterock, nitric acid, and urea via lines 1, 2, and 4, respectively, toreactor 3, in which case the reaction is allowed to proceed attemperatures of about 50°-60° C. for a period of time of about 1 toabout 4 hours.

Still subsequently, the melt in reactor 3 is then passed via line 5 andmeans for control of flow 5a to drum granulator 6, or other granulationdevices familiar to those knowledgeable in this art. After processing ingranulator 6, the product is passed via lines 7, 9, and 11 to dryer 8,cooler 10, and screens 12, respectively. The oversize product is passedvia line 13 to ball mill 14, or other such device, and along with theundersize product via line 15 passed via line 16 to granulator 6. Onsizeproduct is sent via line 17 to storage, not shown. An alternativeprocedure for practice of the instant invention involves partial dryingof the melt prior to granulation, in which case a dryer is placed (notshown) between reactor 3 and granulator 6. If drying is completed withinthe granulator, then a dryer subsequent to the granulator is notrequired.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The process of the present invention and the practice thereof arecapable of producing a variety of products depending upon the grade,storage characteristics, agronomic properties, and handling propertiesrequired by the producer. In general, the physicochemical properties ofthe products are determined by careful control of the molar HNO₃ :CaOacidulation ratio and the molar ratio CO(NH₂)₂ :CaO utilized in themanufacturing process and are strongly dependent upon the ratios of theurea adducts such as: Ca(H₂ PO₄)(NO₃).CO(NH₂)₂, Ca(NO₃)₂.4CO(NH₂)₂,CO(NH₂)₂.H₃ PO₄, Ca(H₂ PO₄)₂.4CO(NH₂)₂, and CO(NH₂)₂.HNO₃ in the finalproduct, as will be demonstrated presently.

In principle, the molar ratios of HNO₃ :CaO and CO(NH₂)₂ :CaO may bevaried over quite wide ranges. A general recipe for the production ofurea-nitric phosphate fertilizer materials based upon the use of one tonof nitric acid (as 100 percent HNO₃) and dependent upon the desiredmolar ratios of HNO₃ :CaO and CO(NH₂)₂ :CaO is given below. ##EQU1##

EXAMPLES

In order that those skilled in the art may better understand how thepresent invention can be practiced, the following examples are given byway of illustration but not necessarily by way of limitation.

The chemicals employed in the test illustrated in these examples were ofreagent grade and were used without further purification, unlessotherwise specified in the specific examples given below. The phosphateore was of Central Florida origin and had the following composition:30.8 percent P₂ O₅, 45.2 percent CaO, 1.21 percent Al₂ O₃, 1.34 percentFe₂ O₃, 0.37 percent MgO, 8.8 percent SiO₂, 3.63 percent F, 0.09 percentK₂ O, 0.66 percent Na₂ O, 3.4 percent total carbon, 70 ppm Cl, 125 ppmU, 96 ppm V, 61 ppm Cr, and 830 ppm TiO₂. The rock was ground to 55.8percent -200 mesh. All acidulations were conducted with 56.8 percentHNO₃ (density: 1.343 g/mL). Chemical analyses were conducted usingstandard AOAC procedures. Critical relative humidity measurements wereconducted using a vacuum system fitted with a U-tube monometerconstructed from 10-mm Pyrex tubing and filled with No. 6428-R15 siliconfluid (density=0.9586 g/mL). Water vapor pressures were measured at25.0° C. over a finely ground 1.00-g sample to which 30 μL (2.9 percent)water had been added. Melting points were measured using anElectrothermal Melting Point Apparatus. X-ray diffraction spectra weremeasured using a Phillips x-ray refractometer.

COMPARATIVE EXAMPLE I

Table 1 below demonstrates the improved physical properties,particularly with regard to moisture stability, which may be achieved byreacting urea with the individual components normally present in nitricacid acidulates of phosphate ore.

                                      TABLE I                                     __________________________________________________________________________    Comparative Examples of Pure Chemical Compounds                               Sample            Melting                                                                            Grade      Critical relative                                                                        Abbreviated                      No. Compound      point, °C.                                                                  N--P.sub.2 O.sub.5 --K.sub.2 O, wt                                                       humidity at 25° C.,                                                               designation                      __________________________________________________________________________    1   Ca(NO.sub.3).sub.2.4H.sub.2 O                                                                42.7                                                                              11.9--0--0 49.9       CaN                              2   Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2                                                      157-161                                                                            34.1--0--0--                                                                             67.9       CaNU                             3   CO(NH.sub.2).sub.2                                                                          132.7                                                                              46.6--0--0 75.0       U                                4   NH.sub.4 NO.sub.3                                                                           169.6                                                                              35.0--0--0 61.9       AN                               5   CO(NH.sub.2).sub.2.HNO.sub.3                                                                158-159                                                                            34.1--0--0 90.3       UN                               6   CO(NH.sub.2).sub.2.H.sub.3 PO.sub.4                                                         114--118                                                                           17.7--44.9--0                                                                            81.9       UP                               7   Ca(H.sub.2 PO.sub.4).sub.2.4CO(NH.sub.2).sub.2                                               75-115                                                                            23.4--29.7--0                                                                            60.3       CaUP                             8   Ca(H.sub.2 PO.sub.4)(NO.sub.3).CO(NH.sub.2).sub.2                                           >360 16.3--27.5--0                                                                            68.9       N                                __________________________________________________________________________

Samples 1, 3, and 4 of Ca(NO₃)₂.4H₂ O, CO(NH₂)₂, and NH₄ NO₃ werereagent-grade compounds and tested without further purification.

"Cal-Urea," Ca(NO₃)₂.4CO(NH₂)₂ (sample No. 2), referred as CaNU, wasprepared by adding 25.00 g of ground Ca(NO₃)₂.4H₂ O to a 200 mL beakerfollowed by the addition of 25.43 g of powdered urea. The calciumnitrate and urea were thoroughly mixed. The sample immediately becamemoist and formed a thick slurry. After standing for several hours, thebeaker was placed in a convection oven at 75° C. for a period of twodays. The sample was then ground to a fine powder and vacuum dried atroom temperature. X-ray and microscopic examination showed the materialto be essentially pure Ca(NO₃)₂.4CO(NH₂)₂.

Urea nitrate, CO(NH₂)₂.HNO₃ (sample No. 5), referred to as UN, wasprepared by adding 72.24 g of 71 percent HNO₃ to an ice-chilled 400-mLbeaker. Urea then was added in small portions with removal of the beakerfrom the ice bath after each addition to allow reaction to occur. Thisprocess was continued until 50.00 g of urea was added. The solution wasallowed to stand at room temperature for two hours. The product wasfiltered and air-dried under suction. It was then recrystallized from 50mL of water, filtered, air-dried under suction, and oven-dried at 75° C.Chemical analysis indicated 22.79 percent urea-N and 11.46 percent NO₃-N (theoretical: 22.76 percent urea-N and 11.38 percent NO₃ -N. Theproduct was identified by x-ray and microscopic examination as ureanitrate.

Urea phosphate, CO(NH₂)₂.H₃ PO₄ (sample No. 6), referred as UP, wasprepared by adding 160.47 g of 85 percent H₃ PO₄ to 76.00 g of granularurea and heating gently until reaction commenced. The heat was turnedoff and the solution allowed to stir for a period of two hours. Theproduct was filtered and recrystallized twice, first from 40 mL and thenfrom 15 mL of water, respectively. The product was air-dried undervacuum suction and then vacuum dried at room temperature. Chemicalanalysis gave 17.7 percent N and 44.8 percent P₂ O₅ (theoretical: 17.7percent N and 44.9 percent P₂ O₅). X-ray and microscopic analysisidentified the product as CO(NH₂)₂.H₃ PO₄.

The urea adduct of monocalcium phosphate, Ca(H₂ PO₄)₂.4CO(NH₂)₂ (sampleNo. 7), or referred to as CaUP, was prepared by adding 25.00 g of Ca(H₂PO₄)₂.H₂ O (referred to as CaP) to a 100-mL beaker followed by theaddition of 23.83 g of powdered urea. The sample was thoroughly mixed togive a moist tacky solid. Enough distilled water was added to form athick slurry. After standing for two hours, the sample was vacuum driedovernight at room temperature, finely ground, and again vacuum driedovernight. X-ray and microscopic examination showed the sample tocontain Ca(H₂ PO₄)₂.4CO(NH₂)₂ as the major phase with minor phaseconsisting of urea phosphate, CO(NH₂)₂.H₃ PO₄.

The triple component adduct, Ca(H₂ PO₄)(NO₃).CO(NH₂)₂ (sample No. 8),which is designated as N, is a new compound discovered by us during thecourse of the investigation that led to the discoveries of the instantinvention. A pure sample of this compound was prepared as follows: 68percent nitric acid (13.1 mL) was added to 12.4 g of powdered hydroxyapatite, Ca₁₀ (PO₄)₆ (OH)₂, and stirred to form a viscous paste. About 2mL of water was stirred into the mixture to make it more fluid. Finelyground urea (12.0 g) was gradually added and stirring was continued forabout 10 minutes. The reaction mixture was then suspended in 300 mL ofacetone and suction filtered on a coarse glass frit. The filter cake waswashed with three 50-mL portions of acetone and dried on the filter atroom temperature to give 19.4 g of dried solid. The product had thefollowing composition: % Ca=15.3, % P=12.0, % C=4.69, % NO₃ -N=4.9, %urea-N=10.9 (theoretical: % Ca=15.33, % P=12.00, % C=4.69, % NO₃-N=5.43, % urea-N=10.85). The P₂ O₅ content of the product was 92.4percent water soluble and 100 percent citrate soluble. The compound didnot melt at temperatures up to 360° C. Its critical relative humiditywas 68.9 percent. The compound exhibited a unique x-ray powderdiffraction pattern as shown in Table I-A below.

                  TABLE I-A                                                       ______________________________________                                        X-Ray Powder Diffraction Pattern of                                           Ca(H.sub.2 PO.sub.4)(NO.sub.3) CO(NH.sub.2).sub.2.sup.a                       d, Å  I/Io         d, Å                                                                             I/Io                                            ______________________________________                                        12.45     100          2.319  7                                               5.12      18           2.178  7                                               4.73      12           2.078  3                                               4.63       8           2.071  3                                               4.61       5           1.991  1                                               4.135      9           1.971  2                                               3.914     20           1.922  3                                               3.902     35           1.829  1                                               3.875     40           1.790  2                                               3.214     27           1.775  4                                               3.170     16           1.691  3                                               3.140     45           1.568  2                                               3.105     20           1.460  1                                               2.915      3           1.397  1                                               2.844.sup.b                                                                             19           1.281  1                                               2.720      2           1.273  <1                                              2.644.sup.b                                                                             14           1.242  <1                                              2.558      2           1.217  1                                               2.505     11                                                                  ______________________________________                                         .sup.a dspacing corrected with NBS No. 640 (Si powder) as internal            standard.                                                                     .sup.b Broad reflection.                                                 

EXAMPLE II

Table II below gives the physicochemical properties of solid urea-nitricphosphate fertilizer products prepared by reacting phosphate rock withnitric acid at a molar ratio, HNO₃ :CaO=1.2, followed by the addition ofurea to give molar ratios of CO(NH₂)₂ :CaO ranging from 1.6 to 3.8.

The samples were prepared as follows: Ground phosphate rock (12.52 g)was weighed into each of twelve 250-mL beakers. Ten mL (13.43 g) of 56.8percent HNO₃ was pipetted into each beaker. A small amount of distilledwater was added to ensure complete wetting of the samples. The sampleswere heated at 65° C. for a period of one hour. Ground urea (9.69,10.91, 12.12, 13.33, 14.54, 15.75, 16.97, 18.17, 19.39, 20.60, 21.81,and 23.03 g, respectively) was added to each beaker to give ratiosurea:CaO of 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, and3.8, respectively. The samples were thoroughly stirred and enoughdistilled water was added to form a thick slurry and to ensure completemixing of the ingredients. The samples then were vacuum dried at roomtemperature, ground to a fine powder and again vacuum dried.

                                      TABLE II                                    __________________________________________________________________________    Properties of Solid Products Prepared by Addition of Urea to 1.2              HNO.sub.3 :CaO Acidulates of Phosphate Rock                                                                 P.sub.2 O.sub.5 solubility,                                                                        Critical                   Sample                                                                            Ratio                                                                              Melting              Water-                                                                            Citrate-         relative humidity          No. urea:CaO                                                                           point, °C.                                                                    Grade  NO.sub.3 --N, %                                                                      soluble                                                                           soluble                                                                            Phases identified.sup.a                                                                   at 25° C.,                                                                      pH.sup.b          __________________________________________________________________________     9  1.6  134-139                                                                              21.5--13.1--0                                                                        5.6    69.5                                                                              81.7 N, CaNU, UN, Q                                                                            46.9     2.36                       (decomposes)                                                         10  1.8  134-137                                                                              22.3--12.8--0                                                                        5.3    64.8                                                                              77.3 N, CaNU, UN, Q                                                                            58.6     2.39                       (decomposes)                                                         11  2.0  135-138                                                                              23.2--12.2--0                                                                        5.2    68.0                                                                              79.5 N, CaNU, UN, CaP,                                                                         59.4     2.46                       (decomposes)                                                         12  2.2  137-139                                                                              23.8--11.7--0                                                                        5.0    69.2                                                                              82.1 N, CaNU, CaUP, Q                                                                          59.3     2.53                       (decomposes)                                                         13  2.4  134-140                                                                              24.8--11.4--0                                                                        4.8    68.4                                                                              81.6 N, CaNU, Q  54.5     2.51                       (decomposes)                                                         14  2.6  129-134                                                                              25.6--11.0--0                                                                        4.7    69.1                                                                              81.8 CaNU, N, UP, Q                                                                            57.3     2.52                       (decomposes)                                                         15  2.8  114-124                                                                              26.3--10.8--0                                                                        4.4    67.6                                                                              81.5 CaNU, N, UP, Q                                                                            53.9     2.55                       (decomposes)                                                         16  3.0   93-121                                                                              27.0--10.2--0                                                                        4.3    69.6                                                                              81.4 CaNU, N, UP, U, Q                                                                         50.1     2.58                       (decomposes)                                                         17  3.2  100-110                                                                              27.6--10.0--0                                                                        4.1    70.0                                                                              83.0 CaNU, N, UP, U, Q                                                                         49.2     2.57                       (decomposes)                                                         18  3.4   87-108                                                                              28.1--9.7--0                                                                         4.1    69.0                                                                              81.4 CaNU, N, UP, U, Q                                                                         44.7     2.59                       (decomposes)                                                         19  3.6  78-92  28.7--9.5--0                                                                         3.9    67.4                                                                              82.1 CaNU, UP, N, U, Q                                                                         45.0     2.54                       (decomposes)                                                         20  3.8  75-84  29.3--9.1--0                                                                         4.0    68.1                                                                              80.2 CaNU, UP, U, N, Q                                                                         44.2     2.56                       (decomposes)                                                         __________________________________________________________________________     .sup.a N = new compound -- Ca(H.sub.2                                         PO.sub.4)(NO.sub.3).CO(NH.sub.2).sub.2 ; CaP = Ca(H.sub.2                     PO.sub.4).sub.2.H.sub.2 O; CaNU = Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2      UN = CO(NH.sub.2).sub.2.HNO.sub.3 ; UP = CO(NH.sub.2).sub.2.H.sub.3           PO.sub.4 ; CaUP = Ca(H.sub.2 PO.sub.4).sub.2.4CO(NH.sub.2).sub.2 ; Q =        quartz.                                                                       .sup.b pH of 1% solution in water.                                       

EXAMPLE III

Table III, infra, gives the physicochemical properties of solidurea-nitric phosphate fertilizer products made by reacting phosphaterock with nitric acid at a molar ratio, HNO₃ :CaO=1.4, followed by theaddition of urea to give molar ratios of CO(NH₂)₂ :CaO ranging from 1.6to 2.8.

The samples were prepared as follows: Ground phosphate rock (10.73 g)was added to each of thirteen 250-mL beakers. Ten mL (13.43 g) of 56.8percent HNO₃ was pipetted into each beaker. A small amount of distilledwater was added to ensure complete wetting of the samples. The sampleswere heated at 65° C. for a period of 2 hours. Ground urea (8.31, 8.83,9.35, 9.87, 10.39, 10.91, 11.43, 11.95, 12.46, 12.98, 13.50, 14.02, and14.54 g, respectively) was added to each beaker to give ratios urea:CaOof 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, and 2.8,respectively. The samples were thoroughly stirred and enough distilledwater added to form a thick slurry to ensure complete mixing of theingredients. The samples were oven-dried overnight at 55° C. and thenvacuum dried, ground to a fine powder, and again vacuum dried.

                                      TABLE III                                   __________________________________________________________________________    Properties of Solid Products Prepared by Addition of Urea to 1.4              HNO.sub.3 :CaO Acidulates of Phosphate Rock                                                                 P.sub.2 O.sub.5 solubility,                                                                        Critical                   Sample                                                                            Ratio                                                                              Melting              Water-                                                                            Citrate-         relative humidity          No. urea:CaO                                                                           point, °C.                                                                    Grade  NO.sub.3 --N, %                                                                      soluble                                                                           soluble                                                                            Phases identified.sup.a                                                                   at 25° C.,                                                                      pH.sup.b          __________________________________________________________________________    21  1.6  >360   21.2--12.7--0                                                                        6.3    79.5                                                                              89.0 N, CaNU, UN, Q                                                                            34.2     2.35              22  1.7  146    21.7--12.5--0                                                                        6.2    79.2                                                                              88.5 N, CaNU, UN, Q                                                                            35.0     2.33                       (softens)                                                            23  1.8  145    22.2--12.2--0                                                                        6.0    81.1                                                                              89.3 N, CaNU, UN, Q                                                                            38.2     2.36                       (softens)                                                            24  1.9  140    22.6--11.9--0                                                                        5.9    80.6                                                                              89.9 N, CaNU, UN, Q                                                                            45.0     2.32                       (decomposes)                                                         25  2.0  141    22.9--11.7--0                                                                        5.8    80.3                                                                              88.9 N, CaNU, UN, Q                                                                            56.3     2.35                       (decomposes)                                                         26  2.1  142    23.3--11.5--0                                                                        5.6    80.0                                                                              88.7 CaNU, N, UN, Q                                                                            56.8     2.37                       (decomposes)                                                         27  2.2  142    23.7--11.3--0                                                                        5.6    80.5                                                                              89.4 CaNU, N, UN, Q                                                                            56.7     2.40                       (decomposes)                                                         28  2.3  142    24.0--11.2--0                                                                        5.4    80.4                                                                              89.3 CaNU, N, UN, CaP,                                                                         58.4     2.39                       (decomposes)                                                         29  2.4  136    25.0--11.0--0                                                                        6.0    81.8                                                                              90.0 CaNU, N, UN, CaP,                                                                         60.9     2.40              30  2.5  136    24.7--10.7--0                                                                        5.4    82.2                                                                              89.7 CaNU, N, UN, CaP,                                                                         60.6     2.42              31  2.6  136    25.2--10.6--0                                                                        5.3    81.1                                                                              88.7 CaNU, UN, N, CaP,                                                                         59.2     2.38              32  2.7  133    25.5--10.5--0                                                                        5.2    80.0                                                                              88.6 CaNU, UN, N, CaP,                                                                         57.7     2.41                       (decomposes)                                                         33  2.8  133    25.9--10.3--0                                                                        5.1    82.5                                                                              90.3 CaNU, UN, CaP, N,                                                                         55.6     2.39                       (decomposes)                                                         __________________________________________________________________________     .sup.a N = new compound--Ca(H.sub.2 PO.sub.4)(NO.sub.3).CO(NH.sub.2).sub.     ; CaP = Ca(H.sub.2 PO.sub.4).sub.2.H.sub.2 O; CaNU =                          Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2 ; UN = CO(NH.sub.2).sub.2.HNO.sub.     ; UP = CO(NH.sub.2).sub.2.H.sub.3 PO.sub.4 ; CaUP = Ca(H.sub.2                PO.sub.4).sub.2.4CO(NH.sub.2).sub. 2 ; Q = quartz.                            .sup.b pH of 1% solution in water.                                       

EXAMPLE IV

Table IV below gives the physicochemical properties of solid urea-nitricphosphate fertilizer produced by reacting phosphate rock with nitricacid at a molar ratio, HNO₃ :CaO=1.6, followed by addition of urea togive molar ratios, CO(NH₂)₂ :CaO, ranging from 2.2 to 4.0. The sampleswere prepared as follows: Phosphate rock (9.39 g) was added to each often 250-mL beakers. Ten mL (10.43 g) of 56.8 percent HNO₃ was added toeach beaker and the resulting acidulates were heated at about 65° C. fora period of one hour. Ground urea (10.00, 10.91, 11.82, 12.72, 13.63,14.54, 15.45, 16.36, 17.27, and 18.18 g, respectively) was added to givemolar ratios urea:CaO of 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8,and 4.0, respectively. The samples were thoroughly stirred and a littledistilled water was added to form a thick slurry and to ensure completemixing. The samples were vacuum dried at room temperature, ground to afine powder, and again vacuum dried.

                                      TABLE IV                                    __________________________________________________________________________    Properties of Solid Products Prepared by Addition of Urea to 1.6              HNO.sub.3 :CaO Acidulates of Phosphate Rock                                                                 P.sub.2 O.sub.5 solubility, %                   Sample                                                                            Ratio                                                                              Melting              Water-                                                                            Citrate-      Critical relative             No. urea:CaO                                                                           point, °C.                                                                    Grade  NO.sub.3 --N, %                                                                      soluble                                                                           soluble                                                                            Phases identified.sup.a                                                                humidity at 25°                                                        C., %      pH.sup.b           __________________________________________________________________________    34  2.2  134-139                                                                              23.9--11.0--0                                                                        5.7    92.7                                                                              95.5 CaNU, N, UN, Q                                                                         48.7       2.34                        (decomposes)                                                         35  2.4  135-139                                                                              24.9--10.5--0                                                                        5.4    90.5                                                                              94.3 CaNU, N, UN, Q                                                                         58.2       2.31                        (decomposes)                                                         36  2.6  133-138                                                                              25.3--10.2--0                                                                        5.3    90.2                                                                              95.1 CaNU, N, UN, Q                                                                         59.1       2.19                        (decomposes)                                                         37  2.8  133-137                                                                              25.9--9.9--0                                                                         5.1    88.9                                                                              91.9 CaNU, N, UN, Q                                                                         60.1       2.32                        (decomposes)                                                         38  3.0  132-136                                                                              26.7--9.6--0                                                                         4.9    90.6                                                                              94.8 CaNU, N, UN, Q                                                                         58.6       2.32                        (decomposes)                                                         39  3.2  133-138                                                                              27.1--9.4--0                                                                         4.7    91.5                                                                              94.7 CaNU, UP, Q                                                                            56.2       2.35                        (decomposes)                                                         40  3.4  133-137                                                                              27.8--9.0--0                                                                         4.7    93.3                                                                              95.6 CaNU, UP, Q                                                                            56.9       2.40                        (decomposes)                                                         41  3.6  124-128                                                                              28.3--8.8--0                                                                         4.6    92.0                                                                              95.5 CaNU, N, UP, Q                                                                         57.6       2.38                        (decomposes)                                                         42  3.8  121-124                                                                              28.8--8.6--0                                                                         4.4    91.9                                                                              94.2 CaNU, UP, Q                                                                            53.4       2.36                        (decomposes)                                                         43  4.0  108-120                                                                              29.3--8.3--0                                                                         4.3    91.6                                                                              96.4 CaNU, UP, Q                                                                            48.4       2.34                        (decomposes)                                                         __________________________________________________________________________     .sup.a N = new compound--Ca(H.sub.2 PO.sub.4)(NO.sub.3).CO(NH.sub.2).sub.     ; CaP = Ca(H.sub.2 PO.sub.4).sub.2.H.sub.2 O; CaNU =                          Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2 ; UN = CO(NH.sub.2).sub.2.HNO.sub.     ; UP = CO(NH.sub.2).sub.2.H.sub.3 PO.sub.4 ; CaUP = Ca(H.sub.2                PO.sub.4).sub.2.4CO(NH.sub.2).sub.2 ; Q = quartz                              .sup.b pH of 1% solution in water.                                       

EXAMPLE V

Table V below gives the physicochemical properties of solid urea-nitricphosphate fertilizer products produced by reacting phosphate rock withnitric acid at a molar ratio, HNO₃ :CaO=1.8, followed by the addition ofurea to give molar ratios, CO(NH₂)₂ :CaO, ranging from 2.2 to 4.0. Thesamples were prepared as follows: Phosphate rock (8.34 g) was added toeach of ten 250-mL beakers. Ten mL (10.43 g) of 56.8 percent HNO₃ wasadded to each beaker and the acidulates were heated at about 65° C. fora period of one hour. Ground urea (8.89, 9.69, 10.50, 11.31, 12.12,12.93, 13.73, 14.54, 15.35, and 16.16 g., respectively) was added togive molar ratios urea:CaO of 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6,3.8, and 4.0, respectively. The samples were thoroughly stirred and alittle distilled water was added to form a thick slurry and to ensurecomplete mixing of the ingredients. The samples were vacuum dried atroom temperature, ground to a fine powder, and again vacuum dried.

                                      TABLE V                                     __________________________________________________________________________    Properties of Solid Products Prepared by Addition of Urea to 1.8              HNO.sub.3 :CaO Acidulates of Phosphate Rock                                                                 P.sub.2 O.sub.5 solubility,                                                                       Critical                    Sample                                                                            Ratio                                                                              Melting              Water-                                                                            Citrate-        relative humidity           No. urea:CaO                                                                           point, °C.                                                                    Grade  NO.sub.3 --N, %                                                                      soluble                                                                           soluble                                                                            Phases identified.sup.a                                                                  at 25° C.,                                                                       pH.sup.b          __________________________________________________________________________    44  2.2  130    24.0--10.5--0                                                                        6.8    95.2                                                                              97.1 N, CaNU, UN, Q                                                                           35.5      2.13                       (softens)                                                            45  2.4  128-131                                                                              24.6--10.2--0                                                                        6.6    96.1                                                                              98.0 N, CaNU, UN, Q                                                                           47.8      2.19                       (decomposes)                                                         46  2.6  128-132                                                                              25.2--9.9--0                                                                         6.4    94.9                                                                              97.0 CaNU, UN, N, Q                                                                           58.0      2.21                       (decomposes)                                                         47  2.8  133-134                                                                              25.8--9.7--0                                                                         6.1    94.8                                                                              96.9 CaNU, UN, N, Q                                                                           59.6      2.18                       (decomposes)                                                         48  3.0  134-135                                                                              26.4--9.2--0                                                                         6.0    96.7                                                                              98.9 CaNU, UN, N, Q                                                                           59.9      2.20                       (decomposes)                                                         49  3.2  128-133                                                                              27.0--9.0--0                                                                         5.8    94.4                                                                              96.7 CaNU, UN, N, Q                                                                           58.3      2.18                       (decomposes)                                                         50  3.4  128-132                                                                              27.7--8.8--0                                                                         5.6    95.5                                                                              97.7 CaNU, UN, N, UP,                                                                         56.7      2.25                       (decomposes)                                                         51  3.6  130-132                                                                              28.1--8.7--0                                                                         5.4    95.4                                                                              97.7 CaNU, UP, N, UN,                                                                         56.6      2.28                       (decomposes)                                                         52  3.8  122-125                                                                              28.7--8.3--0                                                                         5.3    97.6                                                                              100  CaNU, UP, N, Q                                                                           57.1      2.30                       (decomposes)                                                         53  4.0  120-123                                                                              29.0--8.2--0                                                                         5.2    97.6                                                                              100  CaNU, UP, N, Q                                                                           56.3      2.27                       (decomposes)                                                         __________________________________________________________________________     .sup.a N = new compound -- Ca(H.sub.2                                         PO.sub.4)(NO.sub.3).CO(NH.sub.2).sub.2 ; CaP = Ca(H.sub.2                     PO.sub.4).sub.2.H.sub.2 O; CaNU = Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2      UN = CO(NH.sub.2).sub.2.HNO.sub.3 ; UP = CO(NH.sub.2).sub.2.H.sub.3           PO.sub.4 ; CaUP = Ca(H.sub.2 PO.sub.4).sub.2.4CO(NH.sub.2).sub.2 ; Q =        quartz.                                                                       .sup.b pH of 1% solution in water.                                       

EXAMPLE VI

Table VI below illustrates the physicochemical properties of solidurea-nitric phosphate fertilizer products produced by reacting phosphaterock with nitric acid at a molar ratio, HNO₃ :CaO=2.0, followed by theaddition of urea to give molar ratios, CO(NH₂)₂ :CaO, ranging from 2.3to 3.9.

The samples were prepared as follows: Phosphate rock (7.51 g) was addedto each of nine 250-mL beakers. Ten mL (10.43 g) of 56.8 percent HNO₃was added to each sample and the acidulates were heated at about 65° C.for a period of one hour. Ground urea (8.36, 9.09, 9.82, 10.54, 11.27,12.00, 12.72, 13.45, and 14.18 g, respectively) was added to give molarratios urea:CaO of 2.3, 2.5, 2.7, 2.9, 3.1, 3.3, 3.5, 3.7, and 3.9,respectively. Distilled water was added to form a thick slurry and togive good mixing of the ingredients. The samples were allowed to standat room temperature for a period of 2 hours to ensure complete reactionof the urea. The samples then were vacuum dried, ground to a finepowder, and again vacuum dried.

                                      TABLE VI                                    __________________________________________________________________________    Properties of Solid Products Prepared by Addition of Urea to 2.0              HNO.sub.3 :CaO Acidulates of Phosphate Rock                                                                 P.sub.2 O.sub.5 solubility, %                   Sample                                                                            Ratio                                                                              Melting              Water-                                                                            Citrate-      Critical relative             No. urea:CaO                                                                           point, °C.                                                                    Grade  NO.sub.3 --N, %                                                                      soluble                                                                           soluble                                                                            Phases identified.sup.a                                                                humidity at 25°C.,                                                     %          pH.sup.b           __________________________________________________________________________    54  2.3  140    24.2--10.0--0                                                                        7.2    100 100  CaNU, N, UN, Q                                                                         35.5       2.06                        (decomposes)                                                         55  2.5  139    25.0--9.8--0                                                                         6.9    100 100  CaNU, N, UN, Q                                                                         40.9       2.06                        (decomposes)                                                         56  2.7  137    25.6--9.5--0                                                                         6.7     99 100  CaNU, N, UN, Q                                                                         55.6       2.06                        (decomposes)                                                         57  2.9  130    26.2--9.2--0                                                                         6.6     99 100  CaNU, N, UN, Q                                                                         59.2       2.06                        (decomposes)                                                         58  3.1  131    26.7--8.9--0                                                                         6.4    100 100  CaNU, N, UN, Q                                                                         59.8       2.07                        (decomposes)                                                         59  3.3  130    27.2--8.7--0                                                                         6.2     99 100  CaNU, UN, N, Q                                                                         60.0       2.10                        (decomposes)                                                         60  3.5  128    27.6--8.4--0                                                                         6.0    100 100  CaNU, UN, N, Q                                                                         59.1       2.10                        (decomposes)                                                         61  3.7  128    28.2--8.3--0                                                                         5.9     99 100  CaNU, UN, N, Q                                                                         55.4       2.11                        (decomposes)                                                         62  3.9  128    28.6--8.0--0                                                                         5.7    100 100  CaNU, UN, N, Q                                                                         57.2       2.11                        (decomposes)                                                         __________________________________________________________________________     .sup.a N = new compound -- Ca(H.sub.2                                         PO.sub.4)(NO.sub.3).CO(NH.sub.2).sub.2 ; CaP = Ca(H.sub.2                     PO.sub.4).sub.2.H.sub.2 O; CaNU = Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2      UN = CO(NH.sub.2).sub.2.HNO.sub.3 ; UP = CO(NH.sub.2).sub.2.H.sub.3           PO.sub.4 ; CaUP = Ca(H.sub.2 PO.sub.4).sub.2.4CO(NH.sub.2).sub.2 ; Q =        quartz.                                                                       .sup.b pH of 1% solution in water.                                       

EXAMPLE VII

Table VII below gives the physicochemical properties of solidurea-nitric phosphate fertilizer products prepared by reacting phosphaterock with nitric acid at a molar ratio, HNO₃ :CaO=2.1, followed by theaddition of urea to give molar ratios, CO(NH₂)₂ :CaO, ranging from 2.2to 4.0.

The samples were prepared as follows: Ground phosphate rock (7.15 g) wasadded to each of ten 250-mL beakers. Ten mL (10.43 g) of 56.8 percentHNO₃ was added to each sample and the acidulates were heated at about65° C. for a period of one hour. Ground urea (7.62, 8.31, 9.00, 9.69,10.39, 11.08, 11.77, 12.46, 13.16, and 13.85 g, respectively) was addedto give molar ratios urea:CaO of 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6,3.8, and 4.0, respectively. A little distilled water was added to form athick slurry and to give complete mixing of the ingredients. The sampleswere then vacuum dried, ground to a fine powder, and again vacuum dried.

                                      TABLE VII                                   __________________________________________________________________________    Properties of Solid Products Prepared by Addition of Urea to 2.1              HNO.sub.3 :CaO Acidulates of Phosphate Rock                                                                 P.sub.2 O.sub.5 solubility,                                                                        Critical                   Sample                                                                            Ratio                                                                              Melting              Water-                                                                            Citrate-         relative humidity          No. urea:CaO                                                                           point, °C.                                                                    Grade  NO.sub.3 --N, %                                                                      soluble                                                                           soluble                                                                            Phases identified.sup.a                                                                   at 25°C.,                                                                       pH.sup.b          __________________________________________________________________________    63  2.2  >360   23.7--10.2--0                                                                        7.2    99.0                                                                              100  N, CaNU, UN, Q                                                                            34.2     2.11              64  2.4  >360   24.5--9.9--0                                                                         6.9    99.0                                                                              100  N, CaNU, UN, Q                                                                            34.8     2.12              65  2.6  130-134                                                                              25.0--9.5--0                                                                         6.8    100 100  CaNU, N, UN, Q                                                                            41.5     2.10                       (decomposes)                                                         66  2.8  126-131                                                                              25.8--9.3--0                                                                         6.6    100 100  CaNU, N, UN, Q                                                                            55.4     2.13                       (decomposes)                                                         67  3.0  128-131                                                                              26.3--9.0--0                                                                         6.4    100 100  CaNU, N, UN, CaP,                                                                         58.2     2.13                       (decomposes)                                                         68  3.2  125-130                                                                              26.6--8.8--0                                                                         6.2    100 100  CaNU, UN, N, CaP,                                                                         59.5     2.11                       (decomposes)                                                         69  3.4  123-128                                                                              27.3--8.5--0                                                                         6.0    100 100  CaNU, UN, N, CaP,                                                                         59.1     2.13                       (decomposes)                                                         70  3.6  124-127                                                                              27.7--8.3--0                                                                         5.8    100 100  CaNU, UN, N, CaP,                                                                         58.2     2.11                       (decomposes)                                                         71  3.8  121-125                                                                              28.4--8.2--0                                                                         5.8    98.8                                                                              100  CaNU, UN, CaP, N,                                                                         53.4     2.14                       (decomposes)                                                         72  4.0  119-125                                                                              28.7--7.9--0                                                                         5.6    100 100  CaNU, UN, CaP, N,                                                                         56.8     2.15                       (decomposes)                                                         __________________________________________________________________________     .sup.a N = new compound -- Ca(H.sub.2 PO.sub.4)(NO.sub.3).CO(NH.sub.2)        .sub.2 ; CaP = Ca(H.sub.2 PO.sub.4).sub.2.H.sub.2 O; CaNU =                   Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2 ; UN = CO(NH.sub.2).sub.2.HNO.sub.     ; UP = CO(NH.sub.2).sub.2.H.sub.3 PO.sub.4 ; CaUP = Ca(H.sub.2                PO.sub.4).sub.2.4CO(NH.sub.2).sub.2 ; Q = quartz.                             .sup.b pH of 1% solution in water.                                       

INVENTION PARAMETERS

After sifting and winnowing through the data presented in the examplessupra, as well as other data which we have assembled in discovering anddeveloping the present invention, we have determined that the operableparameters of the present invention are as follows:

The mole ratio of nitric acid to calcium oxide present within thephosphate ore must be maintained within the range of about 1:1 to about2:1. The preferred range of the mole ratio HNO₃ :CaO for the productionof N-P fertilizer products with high water-soluble P₂ O₅ contents isbetween 1.2:1 and 2.1:1. The most preferred mole ratio of HNO₃ :CaO forthe production of N-P fertilizer products with 100 percent water-solubleP₂ O₅ content is 2.0:1. However, very high water-soluble P₂ O₅ contentsmay be achieved at lower acidulation ratios as shown by the examples.

The nitric acid-phosphate ore reaction conditions must be maintainedwithin the range of 40° C. to 100° C. for a period of 0.5 to 3 hours.The preferred reaction conditions when acidulation is performed prior tothe addition of urea are: reaction temperature, 60° C. to 70° C., andreaction time, 0.5 to 2 hours. The preferred stirring times after theaddition of urea is 1 to 2 hours. The most preferred nitricacid-phosphate ore reaction condition when acidulation is performedprior to the addition of urea is: reaction temperature, 65° C. andreaction time, 1 hour. The most preferred stirring time after theaddition of urea is 1.5 hours.

The preferred reaction conditions when nitric acid, phosphate ore, andurea are simultaneously added to the reactor are: reaction temperatures50° C. to 60° C. for a period of 1 to 3 hours. The most preferredreaction conditions when nitric acid, phosphate ore, and urea aresimultaneously added to the reactor are: reaction temperature, 55° C.,and reaction time, 2 hours.

The mole ratio of urea:CaO within the reaction mixture must bemaintained within the range of about 1.6-4. The preferred urea:CaO isdependent upon the desired product grade, hygroscopicity, andwater-soluble P₂ O₅ content as demonstrated by Examples II through VII,supra.

The preferred mole ratios, urea:CaO, when the HNO₃ :CaO acidulationratio is 1.2, are 1.6 to 3.8. The most preferred mole ratio urea:CaO is2.2 in order to produce a N-P product of approximate grade 24-12-0, witha critical relative humidity of 59 percent and a P₂ O₅ water solubilityof 69 percent.

The preferred mole ratios, urea:CaO, when the HNO₃ :CaO acidulationratio is 1.4, are 1.6 to 2.8. The most preferred mole ratio urea:CaO is2.4 in order to produce a N-P product of approximate grade 25-11-0 witha critical relative humidity of 61 percent and a P₂ O₅ water solubilityof 82 percent.

The preferred mole ratios, urea:CaO, when the HNO₃ :CaO acidulationratio is 1.6, are 2.2 to 4.0. The most preferred mole ratio urea:CaO is2.8 in order to produce a N-P product of approximate grade 26-10-0, witha critical relative humidity of 60 percent and a P₂ O₅ water solubilityof 89 percent.

The preferred mole ratios, urea:CaO, when the HNO₃ :CaO acidulationratio is 1.8, are 2.2 to 4.0. The most preferred mole ratio urea:CaO is3.0 in order to produce a N-P product of approximate grade 26-9-0, witha critical relative humidity of 60 percent and a P₂ O₅ water solubilityof 97 percent.

The preferred mole ratios, urea:CaO, when the HNO₃ :CaO acidulationratio is 2.0, are 2.3 to 3.9. The most preferred mole ratio urea:CaO is3.3 in order to produce a N-P product of approximate grade 27-9-0, witha critical relative humidity of 60 percent and a P₂ O₅ water solubilityof 100 percent.

The preferred mole ratios, urea:CaO, when the HNO₃ :CaO acidulationratio is 2.1, are 2.2 to 4.0. The most preferred mole ratio urea:CaO is3.2 in order to produce a N-P product of approximate grade 27-9-0, witha critical relative humidity of 60 percent and a P₂ O₅ water solubilityof 100 percent.

From considerations relating to manufacture, storage, transportation,and marketing of fertilizer products, it is normally assumed that theminimum acceptable critical relative humidity for such products shouldbe about 55 percent. Some of the products selected from Tables II-VII,supra, have critical relative humidities slightly below this value buthave been included in the broad claimed ranges because of otherconsiderations.

The most preferred urea-nitric phosphate products prepared from aphosphate rock are summarized in Table VIII below. The selection isbased primarily upon hygroscopicity considerations. Choices among theseproducts will depend upon the desired grade and required P₂ O₅solubility.

                                      TABLE VIII                                  __________________________________________________________________________    Summary of Most Promising Urea-Nitric Phosphate Products                                                P.sub.2 O.sub.5 solubility, %                       Acidulation ratio                                                                      Ratio       Melting                                                                            Water-                                                                            Citrate-                                                                           pH of 1%                                                                            Critical relative                    HNO.sub.3 :CaO                                                                         urea:CaO                                                                           Grade  point, °C.                                                                  soluble                                                                           soluble                                                                            solution                                                                            humidity at 25° C.,           __________________________________________________________________________                                             %                                    1.2      2.2  23.8--11.7--0                                                                        137-139                                                                            69.2                                                                              82.1 2.5   59.3                                 1.4      2.4  25.0--11.0--0                                                                        136  81.8                                                                              90.0 2.4   60.9                                 1.6      2.8  25.9--9.9--0                                                                         133-137                                                                            88.9                                                                              91.9 2.3   60.1                                 1.8      3.0  26.4--9.2--0                                                                         134-135                                                                            96.7                                                                              98.9 2.1   59.9                                 2.0      3.3  27.2--8.7--0                                                                         130  99.0                                                                              100  2.1   6.0                                  2.1      3.2  26.6--8.8--0                                                                         125-130                                                                            100 100  2.1   59.5                                 __________________________________________________________________________

While we have shown and described particular embodiments of ourinvention, modifications and variations thereof will occur to thoseskilled in the art. We wish it to be understood, therefore, that theappended claims are intended to cover such modifications and variationswhich are within the true scope and spirit of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:
 1. A new composition of matter having the molecularformula, Ca(H₂ PO₄)(NO₃).CO(NH₂)₂, and having the following x-ray powderdiffraction pattern:

    ______________________________________                                        d, Å I/Io          d, Å                                                                             I/Io                                            ______________________________________                                        12.45    100           2.319  7                                               5.12     18            2.178  7                                               4.73     12            2.078  3                                               4.63      8            2.071  3                                               4.61      5            1.991  1                                               4.135     9            1.971  2                                               3.914    20            1.922  3                                               3.902    35            1.829  1                                               3.875    40            1.790  2                                               3.214    27            1.775  4                                               3.170    16            1.691  3                                               3.140    45            1.568  2                                               3.105    20            1.460  1                                               2.915     3            1.397  1                                               2.844    19            1.281  1                                               2.720     2            1.273  <1                                              2.644    14            1.242  <1                                              2.558     2            1.217  1                                               2.505    11                                                                   ______________________________________                                    


2. A method for the preparation of solid urea nitric phosphatefertilizer products having agronomically advantageous low pHs rangingfrom about 1 to about 4 and having enhanced storage characteristicsincluding high critical relative humidity, which process comprises thesteps of:(1) introducing into a reactor nitric acid and finely dividedparticulate phosphate rock in proportions such that the mole ratio ofHNO₃ :CaO introduced and maintained in said reactor ranges from about1.2 to about 2.1; (2) maintaining the materials introduced into saidreactor for a period of time ranging from about 30 minutes to about 2hours at temperatures ranging between about 60° C. and about 100° C.;(3) subsequently introducing into said reactor urea in proportions suchthat the mole ratio of urea:CaO in said reactor is adjusted to the rangeof between about 1.6 to about 4; (4) maintaining the resulting materialsin said reactor for a period of time ranging between about 1 and about 2hours and at a temperature ranging from about 30° C. to about 70° C.;and (5) removing from said reactor the resulting urea nitric phosphateslurry to granulating, drying and sizing steps, respectively, wherefromsaid sizing step is recovered onsize particulate urea nitricphosphate;said product urea nitric phosphate characterized by the factthat the critical relative humidity thereof ranges upwards to about 60percent, and the P₂ O₅ water solubility thereof ranges upwards fromabout 70 percent.
 3. The process of claim 2 wherein said HNO₃ :CaOacidulation mole ratio is about 1.2, wherein said urea:CaO mole ratioranges between about 1.6 to about 3.2, wherein said urea nitricphosphate fertilizer product the critical relative humidity ranges fromabout 47 to about 60 percent, and the P₂ O₅ water solubility is about 70percent.
 4. The process of claim 2 wherein said HNO₃ :CaO acidulationmole ratio is about 1.2, wherein said urea:CaO mole ratio ranges betweenabout 1.8 to about 2.6, wherein said urea nitric phosphate fertilizerproduct the critical relative humidity ranges from about 55 to about 60percent, and the P₂ O₅ water solubility is about 70 percent.
 5. Theprocess of claim 2 wherein said HNO₃ :CaO acidulation mole ratio isabout 1.2, wherein said urea:CaO mole ratio ranges between about 2 toabout 2.2, wherein said urea nitric phosphate fertilizer product thecritical relative humidity is about 60 percent, and the P₂ O₃ watersolubility is about 70 percent.
 6. The process of claim 2 wherein saidHNO₃ :CaO acidulation mole ratio is about 1.4, wherein said urea:CaOmole ratio ranges between about 2.0 to about 2.8, wherein said ureanitric phosphate fertilizer product the critical relative humidityranges from about 55 to about 61 percent, and the P₂ O₅ water solubilityis about 80 percent.
 7. The process of claim 2 wherein said HNO₃ :CaOacidulation mole ratio is about 1.4, wherein said urea:CaO mole ratioranges between about 2.4 to about 2.5, wherein said urea nitricphosphate fertilizer product the critical relative humidity is about 61percent, and the P₂ O₅ water solubility is about 82 percent.
 8. Theprocess of claim 2 wherein said HNO₃ :CaO acidulation mole ratio isabout 1.6, wherein said urea:CaO mole ratio ranges between about 2.2 toabout 4.0, wherein said urea nitric phosphate fertilizer product thecritical relative humidity ranges from about 50 to about 60 percent, andthe P₂ O₅ water solubility is about 90 percent.
 9. The process of claim2 wherein said HNO₃ :CaO acidulation mole ratio is about 1.6, whereinsaid urea:CaO mole ratio ranges between about 2.4 to about 3.6, whereinsaid urea nitric phosphate fertilizer product the critical relativehumidity ranges from about 56 to about 60 percent, and the P₂ O₅ watersolubility is about 90 percent.
 10. The process of claim 2 wherein saidHNO₃ :CaO acidulation mole ratio is about 1.6, wherein said urea:CaOmole ratio is about 2.8, wherein said urea nitric phosphate fertilizerproduct the critical relative humidity is about 60 percent, and the P₂O₅ water solubility is about 90 percent.
 11. The process of claim 2wherein said HNO₃ :CaO acidulation mole ratio is about 1.8, wherein saidurea:CaO mole ratio ranges between about 2.4 to about 4.0, wherein saidurea nitric phosphate fertilizer product the critical relative humidityranges from about 50 to about 60 percent, and the P₂ O₅ water solubilityranges from about 94 to about 98 percent.
 12. The process of claim 2wherein said HNO₃ :CaO acidulation mole ratio is about 1.8, wherein saidurea:CaO mole ratio ranges between about 2.6 to about 4.0, wherein saidurea nitric phosphate fertilizer product the critical relative humidityranges from about 56 to about 60 percent, and the P₂ O₅ water solubilityranges from about 96 to about 100 percent.
 13. The process of claim 2wherein said HNO₃ :CaO acidulation mole ratio is about 1.8, wherein saidurea:CaO mole ratio is about 3.0, wherein said urea nitric phosphatefertilizer product the critical relative humidity is about 60 percent,and the P₂ O₅ water solubility is about 99 percent.
 14. The process ofclaim 2 wherein said HNO₃ :CaO acidulation mole ratio is about 2.0,wherein said urea:CaO mole ratio ranges between about 2.7 to about 3.9,wherein said urea nitric phosphate fertilizer product the criticalrelative humidity ranges from about 55 to about 60 percent, and the P₂O₅ water solubility ranges from about 99 to about 100 percent.
 15. Theprocess of claim 2 wherein said HNO₃ :CaO acidulation mole ratio isabout 2.0 wherein said urea:CaO mole ratio is about 3.3, wherein saidurea nitric phosphate fertilizer product the critical relative humidityis about 60 percent, and the P₂ O₅ water solubility is about 99 percent.16. The process of claim 2 wherein said HNO₃ :CaO acidulation mole ratiois about 2.1, wherein said urea:CaO mole ratio ranges between about 2.8to 4.0, wherein said urea nitric phosphate fertilizer product thecritical relative humidity ranges from about 55 to about 60 percent, andthe P₂ O₅ water solubility ranges from about 98 to about 100 percent.17. The process of claim 2 wherein said HNO₃ :CaO acidulation mole ratiois about 2.1, wherein said urea:CaO mole ratio ranges between about 3.2to about 3.4, wherein said urea nitric phosphate fertilizer product thecritical relative humidity ranges from about 59 to about 60 percent, andthe P₂ O₅ water solubility is about 100 percent.